In manufacturing semiconductor devices, semiconductor wafers are repeatedly subjected to various processes such as a film forming process, an etching process or the like in order to manufacture desired devices. Recently, semiconductor devices have been required to have high speed, a fine wiring pattern, and a high level of integration. In this regard, a wiring needs to have lower resistance (improvement in conductivity) and more enhanced electromigration tolerance.
In accordance with these needs, copper (Cu) having higher electromigration tolerance and higher conductivity (lower resistance) than aluminum (Al) or tungsten (W) has been employed as a wiring material.
A copper wiring is formed by forming trenches or holes in an interlayer insulation layer and burying copper in the trenches or holes. In this case, a barrier film is formed prior to burying copper in order to prevent diffusion of copper into the interlayer insulation layer.
Although films formed of tantalum (Ta), titanium (Ti), tantalum nitride (TaN) or titanium nitride (TiN) by physical vapor deposition (PVD) have been used as the barrier film, these films may not provide sufficient step coverage as a wiring pattern is gradually being miniaturized. Thus, in recent years, a MnOx film, which can be formed into a thin film with good step coverage by using a chemical vapor deposition (CVD) method, has been suggested as the barrier film. However, since the MnOx film exhibits low adhesion to a copper film, there is proposed a method in which a ruthenium (Ru) film having high adhesion to copper is first formed on the MnOx film and then a copper film is formed on the ruthenium film to form a copper wiring.
On the other hand, since a good quality ruthenium film is difficult to obtain due to low nucleation density of ruthenium in forming the ruthenium film on the MnOx film, there is proposed a technology in which hydrogen radical treatment is performed after forming a MnOx film and then the ruthenium film is formed.
However, along with the progress of the miniaturization of a semiconductor device, recess portions such as trenches or the like have an increased aspect ratio. This makes it difficult to form a good quality ruthenium film on a MnOx film in the recess portions. Thus, due to an insufficient burying property of copper, there is a possibility that poor burying occurs.